Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range. Night-useful spectral range techniques may allow sensing radiation that is invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation such as near-infrared or ultraviolet radiation.
A liquid crystal display (LCD) may be based on one or more circuit platforms such as PCB (printed circuit board) with one or more illumination sources such as LED (light emitting diodes), CCFL (cold cathode fluorescent lamps), Electro-luminescent panel, etc. An LCD display may be illuminated by one or more illumination methods such as a side illumination source, a peripheral illumination source, an array illumination source, a matrix illumination source, etc. In addition, LCD panels may use a light diffuser such as a light guide. A light guide may be made from materials such as acrylic resin, polycarbonate, epoxies, and/or glass that diffuses light emanating from the illumination source, such that the light may be evenly spread across the panel.
U.S. Patent Application Publication No. 2014/036533 to Smith Gillespie discloses LCD backlighting systems, and particularly LCD backlighting systems used in connection with night vision systems. The LCD backlighting systems may be configured to achieve reduced cost, reduced volume, and other desirable outcomes by use of a dual-mode configuration. In a dual-mode configuration, certain light sources are active in both day mode and night mode operation. Night mode light sources may be IR filtered in order to prevent disruption of operation of night vision equipment
U.S. Pat. No. 6,111,622 to Abileah discloses a backlit liquid crystal display device having improved nighttime operational characteristics. The backlit liquid crystal display device includes a fluorescent lamp for daytime operation and a separate light source for nighttime operation which emits a low-intensity light. Preferably, the nighttime light source may be an electroluminescent panel which also acts as a daytime reflector of light. An integral image-splitting and collimating lens is provided to increase the uniformity of the light emitted and to provide wide angle view ability. A sharp cut-off IR filter may also be included in the device to provide NVIS-B night vision goggle compatibility.
U.S. Pat. No. 5,143,433 to Farrell discloses LCD designed with backlighting systems which presents a way to provide night vision viewing compatibility of backlit electro-optic modulated light valve or LCD displays designed for daylight viewing. LCD designed with backlighting systems may provide a high brightness, good contrast display under daylight conditions are inappropriate for use in dark, night time conditions where viewing of the display may be desired utilizing electronic night vision equipment. LCD designed with backlighting systems describes improvements to standard backlighting displays which through the utilization of arrays of low-level intensity light sources such as secondary fluorescent light sources, miniature incandescent lamps or light emitting diodes, the general means used in daylight vision can be turned off and the secondary low-level lighting sources achieve a minimum intensity acceptable for night vision electronic viewing.
U.S. Pat. No. 5,211,463 to Kalmanash discloses a backlight system for liquid crystal device display which may be equipped with a dual lighting system for day viewing and compatible with night vision systems. The day lighting system uses conventional fluorescent or incandescent lamps for full color display during daytime use. The night lighting system uses a light source which may be either filtered to remove infrared and near infrared wavelengths or which may be chosen from a class of sources which does not emit such wavelengths. The day lighting system is disabled while the night system is in use.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.